Method of manufacturing fuel pellet

Purpose: To manufacture UO2 fuel pellets at high sintering density under low temperature and low pressure sintering conditions. Method: At first in a TBP solvent extraction step, impurities are removed from refined uranium ores (crude U3O8) to prepare UO2(NO3)2. Then, UO3 as intermediate substance is prepared in evaporation and denitration step. Then, UO3 is brought into reaction with HNO3 to prepare ADU (ammonium diuranate), which is dried and reduced to prepare a UO2 powder. The UO2 powder prepared directly from UO3 not by way of UF6 gases (direct conversion UO2) has sintering property of high activity. Pellets are molded by using the direct conversion UO2. Since the direct conversion UO2 has high activity, pellets with the sintering density as high as 97 % or greater can be obtained even under a molding pressure of about 1 ton/cm2. (Ikeda, J.)